[fsp] Buffer consecutive Write() calls.

chrome/browser/chromeos/file_system_provider/fileapi/file_stream_writer.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/file_system_provider/fileapi/file_stream_writer.h"
 
 #include "base/debug/trace_event.h"
 #include "base/memory/ref_counted.h"
+#include "base/thread_task_runner_handle.h"
 #include "chrome/browser/chromeos/file_system_provider/fileapi/provider_async_file_util.h"
 #include "chrome/browser/chromeos/file_system_provider/mount_path_util.h"
 #include "chrome/browser/chromeos/file_system_provider/provided_file_system_interface.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
 
 using content::BrowserThread;
 
 namespace chromeos {
@@ skipping 246 matching lines @@
       FROM_HERE,
       base::Bind(&OperationRunner::AbortOnUIThread,
                  runner_,
                  base::Bind(&FileStreamWriter::OnAbortCompleted,
                             weak_ptr_factory_.GetWeakPtr(),
                             callback)));
   return net::ERR_IO_PENDING;
 }
 
 int FileStreamWriter::Flush(const net::CompletionCallback& callback) {
-  if (state_ != INITIALIZED)
-    return net::ERR_FAILED;
+  base::ThreadTaskRunnerHandle::Get()->PostTask(
+      FROM_HERE,
+      base::Bind(callback, state_ == INITIALIZED ? net::OK : net::ERR_FAILED));
 
-  return net::OK;
+  return net::ERR_IO_PENDING;
 }
 
 void FileStreamWriter::OnWriteFileCompleted(
     int buffer_length,
     const net::CompletionCallback& callback,
     base::File::Error result) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK_EQ(INITIALIZED, state_);
 
   if (result != base::File::FILE_OK) {
@@ skipping 40 matching lines @@
                  current_offset_,
                  buffer_length,
                  base::Bind(&FileStreamWriter::OnWriteFileCompleted,
                             weak_ptr_factory_.GetWeakPtr(),
                             buffer_length,
                             callback)));
 }
 
 }  // namespace file_system_provider
 }  // namespace chromeos